Emacs as a programming IDE

Marie-Hélène Burle

November 14, 2023

Why I still use (and love) Emacs

Yes, there are much simpler text editors, but they pale in comparison (apart from Vim)

And yes, there are now excellent IDEs for Python, Julia, and R without Emacs learning curve

So here are a few of my reasons:

Fully customizable
Key-bindings for everything
Undoing/redoing with undo-tree
Opening files
Bookmarking
Searching and navigation within files with helm
Search and replace with regexp
Creation of code snippets with yasnippet
Can be used for Emails, Slack, Telegram with mu4e, emacs-slack, telega

Example: undo/redo

Linear systems: classic undo/redo

flowchart TD
   1((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Have some file

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make some edits

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make more edits

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" "))---4((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make more edits

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" ")):::current---4((" "))
   classDef current stroke: #f96, stroke-width: 2px

Can undo

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" ")):::current---3((" "))---4((" "))
   classDef current stroke: #f96, stroke-width: 2px

Undo some more

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" ")):::current---4((" "))
   classDef current stroke: #f96, stroke-width: 2px

Can redo

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" "))-.-4((" ")):::lost
   3((" "))---5((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px
   classDef lost stroke-dasharray: 3 4

Make new edits

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" ")):::current-.-4((" ")):::lost
   3((" "))---5((" "))
   classDef current stroke: #f96, stroke-width: 2px
   classDef lost stroke-dasharray: 3 4

Can still undo

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" ")):::current---3((" "))-.-4((" ")):::lost
   3((" "))---5((" "))
   classDef current stroke: #f96, stroke-width: 2px
   classDef lost stroke-dasharray: 3 4

Can still undo

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" ")):::current-.-4((" ")):::lost
   3((" "))---5((" "))
   classDef current stroke: #f96, stroke-width: 2px
   classDef lost stroke-dasharray: 3 4

And can redo

Linear systems: classic undo/redo

flowchart TD
   1((" "))---2((" "))---3((" "))-.-4((" ")):::lost
   3((" "))---5((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px
   classDef lost stroke-dasharray: 3 4

But some edits are forever lost

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1)):::current
   classDef current stroke: #f96, stroke-width: 2px

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2)):::current
   classDef current stroke: #f96, stroke-width: 2px

Make some edits

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3)):::current
   classDef current stroke: #f96, stroke-width: 2px

Make more edits

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3))---4((4)):::current
   classDef current stroke: #f96, stroke-width: 2px

Make more edits

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3))---4((4))---5((3)):::current
   classDef current stroke: #f96, stroke-width: 2px

The first undo adds a new point to the chain of edits

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3))---4((4))---5((3))---6((2)):::current
   classDef current stroke: #f96, stroke-width: 2px

More undoing keeps adding points to the chain

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3))---4((4))---5((3))---6((2))---7((3)):::current
   classDef current stroke: #f96, stroke-width: 2px

There is no redo: you stop undoing, then start again to undo the undo

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3))---4((4))---5((3))---6((2))---7((3))---8((5)):::current
   classDef current stroke: #f96, stroke-width: 2px

You can make new edits

Nothing ever gets lost, but you might get headaches

Example: let’s go back to the starting point

Linear systems: Emacs

%%{init: { 'flowchart': {'rankSpacing':15} } }%%
flowchart TD
   1((1))---2((2))---3((3))---4((4))---5((3))---6((2))---7((3))---8((5))---9((3))---10((2))---11((3))---12((4))---13((3))---14((2))---15((1)):::current
   classDef current stroke: #f96, stroke-width: 2px

Non linear system: undo-tree

flowchart TD
   1((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make some edits

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make some edits

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" "))---4((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make some edits

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" ")):::current---4((" "))
   classDef current stroke: #f96, stroke-width: 2px

Undo

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" ")):::current---3((" "))---4((" "))
   classDef current stroke: #f96, stroke-width: 2px

Undo

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" ")):::current---4((" "))
   classDef current stroke: #f96, stroke-width: 2px

Redo

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" "))---4((" "))
   3((" "))---5((" ")):::current
   classDef current stroke: #f96, stroke-width: 2px

Make new edits

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" "))---4((" "))
   3((" ")):::current---5((" "))
   classDef current stroke: #f96, stroke-width: 2px

Undo

Non linear system: undo-tree

flowchart TD
   1((" "))---2((" "))---3((" "))---4((" ")):::current
   3((" "))---5((" "))
   classDef current stroke: #f96, stroke-width: 2px

Switch branch and redo the old version

Non linear system: undo-tree

flowchart TD
   1((" ")):::current---2((" "))---3((" "))---4((" "))
   3((" "))---5((" "))
   classDef current stroke: #f96, stroke-width: 2px

Nothing gets lost and it is more sane to navigate the history

Emacs with Python

Emacs comes with a Python mode that provides syntax highlighting. For a full IDE experience, there are multiple options, the most popular of which being the elpy package

Emacs with R

R is—as Emacs—GNU software and has been integrated with Emacs via the ESS (Emacs Speaks Statistics) package for a very long time

Emacs with Julia

The julia-mode package provides syntax highlighting and the julia-repl package implements a fully functional Julia REPL, optionally with the emacs-libvterm package

ESS also provides an IDE for Julia, but it does not allow for the funky Julia-specific REPL

Another sophisticated option is to use julia-mode with the julia-snail package

Time for a demo